They are singularly focused to avoid the pain. 

There's another set of people who go to pains to cross every T and dot every I.

Holding onto a HELOC long term is painful, so you'll want to make sure your exit from the HELOC is planned out. 

You will also need a team that knows how to work with CMHA, which in itself is a huge pain to deal with.

Also, any advice for avoiding those unexpected surprises (or at least making them less painful) would be super appreciated.

Years ago, my elderly neighbor expressed his concern to me about our trees leaning towards his home and that he wasn't trying to be a pain. 

A 1031 exchange is NOT available for owner occupied property so that’s the bad news.The good news is for owner occupied primary residences, for married couples, the first $500,000 of pain is tax free.No need to worry about a 1031, live in the house, sell it, use the $500,000 exclusion and you pay KP tax on whatever profit may exist,2.

What pain points or problems have you encountered or seen when evaluating real estate deals?

Don't buy the cheapest Amazon sets as it's a pain when they inevitably break.

Most of the negative feedback on BBB has to do with their lack of responsiveness, which could be a growing pain issue since they are affiliated with at least several large REI groups that I am aware of, so are presumably overwhelmed with new business right now.